graeco,
I never checked but I would think the browser based platform would take up the least amount of space on a hard drive.
I like the stand alone (java script version) for logging on. I have a 'trader work station' icon on my desktop and I click on it. enter my username and password and I up and running pretty quickly that way. You must download and run the java script. (there is a link provided for it under IB's instructions.)
On weekends TWS is often inaccessible and also around midnight.(click on trading sytem / system staus for the hours) Best I can remember, when I first moved to IB, I couldn't alway get the demo to work. I did however get it to work enough times to train on it and familiarize myself with it's order entry, procedures. Trading futures, all order entry has to be done from the command line, (at least it did when I signed on) so I wanted to become comfortable with it before using it to put my $ in the market.
If you are still having problems with it tomorrow, you can use IB chat or IB email and they usually respond within reasonable time. I had a couple of questions and I think it was the chat that I used with good results.
Also, anytime you want, feel free to click on my name beside one of my posts and send me a private message or e-mail with any questions that you might have. If I can't give you a good answer, maybe I can help you find someone who can. I usually don't check my email or private messages during trading hours, but sometimes do during midday doldrums.
Best regards and don't give up.
plumlazy